Telegraph repeater



J. HERMAN TELEGRAPH REPEATER Oct. s, 926. 1,601,799

Filed Dec. 11, 1925 ATTORNEY Patented Oct. 5, 1926.

UNITED STATES v 1,601,799 PATENT. OFFICE.

JOSEPH HERMAN, OF NEW YORK N. .Y., ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEGRAPH REPEATER.

' Application filed December 11, 1925. Serial No. 74,863.

This invention relates to telegraph systems, and more particularly to improvements in arrangements for repeating or retransmitting signals in such systems.

When a long telegraph line interconnects two distant stations, it is often desirable to insert in the line'repeater sets to retransmit the signals. Among the types of repeater sets commonly utilized for this purpose are those which utilize two sets of polar relays for repeating the signals. The sets of polar relays have two sets of windings, one set being included in the line or loop circuit and the other set being included in a local or biasing circuit. A type of repeater of this sort may be found in the United StatesPatent No. 1, 17 9,430 issued January 1, 1924, to J. M. Fell. The line or loop circuits in such repeater sets may often vary in length and electrical characteristics due sometimes to the apparatus connected thereto at various places. It is desirable in the operation of these sets that the current in the local or biasing circuits should build up or diedown atthe same rate or inthe same time as the cur-- rent in the line circuits, otherwise the relay arrangements tend to operate falsely and the repeaters will not operate in asatisfactory manner. Accordingly, it is the primary object of this invention to provide arrangements in repeater sets having relays controlled both by a line circuit and a biasing circuit, whereby the rate at which these currents build up in their respective circuits may be equalized and adjusted so that the relay mechanism and the repeater itself will give satisfactory operation. Other objects and features of the invention will appear more fully from the detailed description thereof hereinafter given. y Y

The invention may be more fully understood from the following description, together with the accompanying drawing, in the figure of which is illustrated one form of embodiment of the invention.

In the drawing are shown two stations A and B interconnected by the lines L and L through a repeater set R. -The terminal stations comprise sounder circuits, transmitting keys and sending batteries The repeater set comprises two sets of polar relays 1, 2 and 3, 4. Relays 1 and 2 have operating windings included in the loop circuit 5 connected to line L and controlled by the key K and the sending battery at station A. Relays 3 and l have operating windings included in the loop circuit 6 connected to line L, and controlled by the battery and keyK at station B. The strength of the operating current in these circuits may, for purposes of illustration, be assumed to be milliamperes. The relays 1 and 2 also have biasing windings included in a biasing circuit 7 which extends from negative battery 10, contact of relay' l, the two resist ance elements 13, windings of relays 1 and 2, conductor 7 to ground 9. Connected in parallel with the resistance elements 13 and negative battery 10 is the resistance'lT and the positive battery 11. The resistance 17 is greater than resistance elements 13. For example, the value of both the resistance elements 13 may be assumed to be 2000 ohms and the value of resistance 17 may be assumed to be 4000 ohms. Since the batteries 10 and 11 each have a voltage of 120 volts, a negative current of 30 milliamperes will flow through the auxiliary or biasing windings of relays 1 and 2. Under these conditions, when the loop circuit 5 is closed, the relays 1 and2 will keep their arinatures on their marking contacts due to the effect of the 60 milliampere current through the operating windings even though the effect of this current is opposed by the effect of the current through the auxiliary windings, which under the combined effect of batteries 10 and 11 and resistances 13 and 17, would tend'to operate the contacts to spacing. The operating and biasing windings of relays 3 and 4t and theloop circuit 6 and the biasing circuit 8 are arranged in a similar manner to those of relays 1 and 2. In other -words, if the loop circuits 5 and 6 are both closed, then all four relays will have their armatures on the marking contacts. Under this condition current flowing through the relay windings in the loop circuits will tend to hold the armatures to their marking contacts while current flowing through the auxiliary windingswill tend to move the armatures to their spacing contacts. Since the tendency to, spacing is due to a current of only 30 milliamperes, while the tendency to marking is due to 60 milliamperes, the armatures will stay on the markingcontacts.

If signals are now transmittedinto the loop ,5'by opening and closing that loop by the key K,, then the current through the operating windings of relays 1 and 2 will be interrupted. Consequently, the armatures of these relays will move to their spacing contacts under the influence of the current of 30 milliamperes in the auxiliary windings. As a result of this operation, the armature of relay 2 has opened the loop circuit 6, and the armature of relay 1 has removed the positive bias ng battery from the auxiliary windings of relays 3 and 4. The removal of the biasing battery causes a holding current of 30 milliamperes to flow through the auxiliary windings of relays 3 and 4. This is due to the negative 120-volt battery 10 which is connected to these windings through the resistance 16, which is of 4000 ohms. The armatures of relays 3 and 4 will, therefore, remain on their marking contacts in spite of the fact that the previous holding current in loop 6 has dropped from 60 milliamperes to zero. This operation will be repeated every time loop 5 is opened.

"The conditions described above may be stated briefly as follows: Whenever a spacing signal is present in loop 5, a holding current of 30 milliamperes nows througl'i the auxiliary windings of relays 3 and 4, and whenever a marking signal is present in the loop, a biasing current of 30 milliamperes flows through the auxiliary windings. The latter current is due to the fact that the holdingcurrent is overpowered by a current from a battery of opposite polarity, which flows through a lower resistance,

namely, the resistance 12, than does the holding current which flows through resistance 16, and, therefore, reverses the direction of the current flowing through the auxiliary windings. I

, If the operator connected to loop 6 wishes to interrupt the operator connected to loop 5, he opens his key K,. At the instant when the armatures of relays 1 and 2 rest on their marking contacts, due to the transmission of a marking signal by the operator connected to loop 5, the armatures of relays 8 and 4 move to their spacing contacts. This is due to the fact that the current in the auxiliary windings of relays 3 and 4 has been changed from a marking to a spacing current, while the usual marking current of 60 milliamperes in loop 6 is reduced to zero becauseof the open key in that loop. Relays 3 and 4, therefore, remain on their spacing contacts, keeping loop 5 open, and holding relays 1 and 2 to their marking contacts. The latter effect is due to the removal of the negative biasing battery by relay 4. As soon as the operator in loop 5 notices that his loop circuit is open, he closes his key K and the operator in loop 6 can send.

It will be seen that the apparatus and its operation in one loop circuit is identical with that of the apparatus in the other loop circuit. The only'unasymmetrical feature is the use of a positive battery for holding in the auxiliary circuit of one set of relays and a negative battery for the same purpose in the auxiliary circuit of the other set of relays. This is done to permit the use of a common battery tap in the auxiliary circuits of the two sets of relays without cau ing an appreciable variation in voltage because of the common resistance.

A repeater of the type heretofore described may be found in the United States Patent 1,479,430, issued January 1, 1924, to J. M. Fell, and reference may be had thereto for a more complete disclosure. It will be seen that the loop circuits such as 5 and 6 may difier considerably in their electrical characteristics from their respective biasing circuits '7 and 8. This may be due to the fact that they have a large amount of apparatus, such as relays, connected thereto. Accordingly, it will be seen that because of the difiierence between the electrical characteristics of a loop circuit and its associated biasing'circuit, it may take an appreciable difference in time for the currents to build up to their full strength in these circuits. To illustrate wherein this might have a bad effect upon the operation of the repeater, it is pointed out that when the loop circuit is opened, it causes the armatures of relays 1 and 2 to be moved to their spacing contacts and opens the loop circuit 6 and the biasing circuit 8 which is connected to the positive battery 11. If the loop circuit 5 is now closed again, the loop circuit 6 and the biasing circuit 8 to battery 11 will again be closed. If the current from battery 11 should build up to its full strength of 30 milliamperes before the current in the loop circuit 6, which, at its full strength is 60 milliamperes, should build up to the 30 milliampere point, it will be seen that the relays 3 and 4 would cause their armatures to mo mentarily move to spacing- In other words, the realys 3 and 4 might have a tendency to chatter and thus break up the signals com ing in over the loop circuit 5. Accordingly, it will be seen that the building up of the current in the biasing circuit 8 from the battery 11 should simulate to a large extent the building up of the current in the loop circuit 6. Accordingly, there is connected to ground from the midpoints of the resistance elements 12, a condenser 14. As is well known, the connection to ground of a con denser from the midpoints of a resistance in a circuit serves to act as an electrical retarding means to the building up of the current at the distant end of such a circuit. Accordingly, the building up of the current from the battery 11 through the biasing circuit 8 will be sufficiently retarded by this means, so that it'willnot get ahead of the currentelfect in the loop circuit 6. A similar condenser 15 1S connectedfrom the midpoints of the resistance elements 13 to ground in the biasing circuit 7 to delay the building up of the current in'the biasing circuit 7, so that it will not precede the efl'ect of the current of the loop circuit 5. Accordingly, by placing these electrical retarding means in the biasing circuits, it is possible to control the building up of the currents therein, so that they will not interfere with the proper operation of the relays. Accordingly, by providing the electrical retarding means of this invention, it is pos sible to insure the proper operation of a repeater circuit of this type.

Accordingly, while the invention has been illustrated as embodied in certain specific forms, which are deemed desirable, it is understood that it is capable of embodiment in many other forms without departing from the spirit of the invention as, defined in the appended claims.

What is claimed is:

1. A telegraph repeater comprising relay means controlled jointly by circuits having difierent electrical characteristics, and electrical retarding means associated with one of said circuits for regulating the rate at which the current therein will build up.

2. A telegraph repeater comprising polar relays having two sets of windings, a loop circuit including one of said sets of windings, an auxiliary circuit including another of said sets of windings, the electrical characteristics of said loop circuit and said auxiliary circuit being different, and electrical retarding means in said auxiliary circuit for regulating the rate at which the current therein will build up.

3. A telegraph repeater comprising polar relays having two sets of windings, a loop circuit including one of said sets of windings, an auxiliary circuit including another of said sets of windings, the electrical characteristics of said loop circuit and said auxiliary circuit being different, and electrical retarding means in said auxiliary circuit for regulating the rate at which the current therein shall build up, said electrical retarding means comprising a plurality of resistance elements and a condenser connected to groundfrom the midpoint thereof.

4. A telegraph repeater comprising polar relays having two sets of windings, a loop circuit including one of said sets of windings, an auxiliary circuit including another of said sets of windings, the electrical characteristics of said loop circuit and said auxiliary circuit being difierent, means to open and close said circuit simultaneously, and electrical retarding means in said auxiliary circuit for equalizing the time in which the currents in both of said circuits build up.

5. A telegraph repeater comprising relay means under the joint control of two circuits having difierent electrical characteristics, means for opening and closing said circuits simultaneously, and electrical re-' tarding means in one of said circuits for equalizing the time in which the currents in said circuits build up.

In testimony whereof, I have signed my name to this specification this 10th day of December, 1925.

JOSEPH HERMAN. 

